Systems and methods for uniform expansion and heat setting of medical devices

ABSTRACT

Systems and methods for uniformly expanding and heat setting medical devices. One method can include expanding a medical device by advancing the medical device over a preheated expander, the medical device being uniformly expanded as the medical device is advanced over the preheated expander; and heat setting the expanded medical device while the medical device is positioned over the expander, the preheated expander being maintained at a predetermined heat-setting temperature. The preheated expander can be positioned within a thermal chamber that maintains the preheated expander at the predetermined heat-setting temperature. The medical device can be physically separated from the preheated expander when the medical device is positioned over the expander and can be comprised of a shape-memory material. The preheated expander can remain heated during the expansion and heat setting of a plurality of medical devices.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/490,266 filed on Jun. 6, 2012, the disclosure of which isincorporated herein by this reference.

BACKGROUND OF THE INVENTION

I. The Field of the Invention

The present invention generally relates to the field of medical devices.More specifically, the present invention relates to methods, systems,and devices for manufacturing a self-expanding medical device.

II. Related Technology

The use of intravascular devices to treat cardiovascular diseases iswell known in the field of medicine. The need for a greater variety ofdevices to address different types of circumstances has growntremendously as the techniques for using intravascular devices hasprogressed. One type of intravascular device is a stent or scaffold.Stents and scaffolds are generally cylindrically shaped intravasculardevices that are placed within an artery (or other vessel within thebody) to hold it open. The device can be used to reduce the likelihoodof restenosis or recurrence of the blocking of a blood vessel and can beplaced within an artery on a permanent basis, such as a stent, or atemporary basis, such as a scaffold. In some circumstances, a stent orscaffold can be used as the primary treatment device where it isexpanded to dilate a stenosis and left in place.

A variety of stent and scaffold designs have been developed. Examplesinclude coiled wires in a variety of patterns that are expanded afterbeing placed within a vessel on a balloon catheter, helically woundcoiled springs manufactured from expandable heat sensitive metals,stents or scaffolds shaped in zig-zag patterns, and self-expandingstents and scaffolds inserted in a compressed state for deployment in abody lumen.

Stents and scaffolds can have various features. For instance, a stent orscaffold can have a tubular shape formed from a plurality ofinterconnected struts and/or legs that can form a series ofinterconnected rings. In the expanded condition, the stent or scaffoldcan have a cylindrical shape to expand in an artery. One material formanufacturing self-expanding stents or scaffolds is nitinol, an alloy ofnickel and titanium.

The conventional approach to manufacture a self-expanding stent orscaffold is to begin by laser cutting the design of the stent orscaffold from a tube having a diameter that is approximately equal tothe desired diameter of the compressed (i.e., unexpanded) stent orscaffold. The tube is then deburred to clean any imperfections due tothe cutting. Once the tube has been deburred, the tube is then expandedto the desired diameter, which is the diameter the stent will maintainwhen left within a body vessel. The tube is then heat set at the desiredexpanded diameter to maintain the tube at that diameter.

Conventionally, expanding the stent or scaffold to the desired expandeddiameter requires an iterative process: The tube is positioned on amandrel having a diameter that is slightly larger than the diameter ofthe compressed tube, thereby expanding the tube. Heat is applied to thetube while the tube is on the mandrel to heat set the tube at the newdiameter. The tube and mandrel are allowed to cool to complete the heatsetting, and the tube is then removed from the mandrel. This process isthen repeated with a slightly larger mandrel to expand the tube further.This iterative process of expanding the tube a little at a time isrepeated until the desired expanded diameter is attained.

Although the conventional manufacturing approach discussed abovegenerally yields acceptable self expanding medical devices, the approachhas some shortcomings. For example, it is cumbersome and time consumingdue, in large part, to the iterative heating and cooling processes. Inaddition, a significant amount of energy is used by heating andreheating the medical device and the mandrel during each iteration.Another shortcoming is that, in many instances, cracks are induced inthe stent or scaffold during conventional manufacturing due to undesiredtorque, tension, expansion, and/or compression.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention relate to the manufacture of medicaldevices including implantable medical devices such as stents orscaffolds.

In one embodiment, a method of manufacturing a medical device caninclude expanding a medical device by advancing the medical device overa preheated expander, the medical device being uniformly expanded as themedical device is advanced over the preheated expander; and heat settingthe expanded medical device while the medical device is positioned overthe expander, the preheated expander being maintained at a predeterminedheat-setting temperature.

In another embodiment, a method of manufacturing a medical device caninclude uniformly expanding a compressed medical device from a firstdiameter to a second diameter using a preheated expander; heat settingthe expanded medical device at the second diameter while the medicaldevice is positioned on the preheated expander; and removing theexpanded medical device from the preheated expander, the steps ofuniformly expanding the compressed medical device, heat setting theexpanded medical device, and removing the expanded medical device allbeing performed while the preheated expander is maintained at apredetermined heat-set temperature.

In another embodiment, a method of manufacturing a medical device caninclude positioning a medical device on a plurality of transportmechanisms; advancing the transport mechanisms distally onto a preheatedexpander positioned within a thermal chamber, thereby causing themedical device to advance distally onto the preheated expander, thetransport mechanisms acting as a bearing-type surface that supports andguides the medical device while maintaining a separation between themedical device and the preheated expander; and uniformly expanding themedical device while the medical device is positioned on the preheatedexpander, the medical device becoming heat set when expanded due to thepreheated expander.

These and the other embodiments presented or envisioned herein providesignificant benefits. One benefit is that the medical device can beexpanded from the compressed size to a final desired size in a singlestep. That is, the medical device can be expanded to the final desiredsize using the systems and methods discussed and envisioned hereinwithout going through an iterative expansion process. As a result, asignificant amount of time can be saved using the inventive systems andmethods compared to the conventional approach.

Another benefit is that the medical device expansion can occur while theexpander mechanisms remain heated. That is, the medical device can bepositioned on the expander mechanism, expanded, heat set, and thenremoved from the expander mechanism, all while the expander mechanism ismaintained at the desired heat-set temperature. As a result, asignificant amount of energy can be saved, as well as an additionalamount of time that would otherwise be required to cool and then reheatthe expander mechanisms, as is done in the conventional approach.

Another benefit is that frictional engagement between the medical deviceand the expander can be reduced or eliminated. As a result, thelikelihood is reduced of damage to the medical device from excessivestresses caused by the expander during expansion of the medical device.

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. In the drawings,like numerals designate like elements. Furthermore, multiple instancesof an element may each include separate letters appended to the elementnumber. For example two instances of a particular element “20” may belabeled as “20a” and “20b”. In that case, the element label may be usedwithout an appended letter (e.g., “20”) to generally refer to everyinstance of the element; while the element label will include anappended letter (e.g., “20a”) to refer to a specific instance of theelement.

FIG. 1 illustrates an exploded view of a system for expanding a medicaldevice according to one embodiment;

FIG. 2 illustrates an assembled view of the system shown in FIG. 1;

FIG. 3 is a perspective view of an expander according to one embodiment;

FIG. 4 is a schematic view of a portion of an advancement guide andcorresponding securing devices according to one embodiment;

FIG. 5 is a cross sectional view of one embodiment of an advancementguide assembly, taken along section line 5-5 of FIG. 1; and

FIGS. 6-14 illustrate various steps of a method for expanding a medicaldevice using the system shown in FIGS. 1 and 2, according to oneembodiment.

DETAILED DESCRIPTION

As used in the specification and appended claims, directional terms,such as “top,” “bottom,” “up,” “down,” “upper,” “lower,” “proximal,”“distal,” and the like are used herein solely to indicate relativedirections and are not otherwise intended to limit the scope of theinvention or claims.

Systems and methods are provided herein for expanding a medical device.The methods provided through the system can allow the medical device tobe expanded from the compressed size to a final desired size in a singlestep. That is, the medical device can be expanded to the final desiredsize using the systems and methods discussed and envisioned hereinwithout going through an iterative expansion process. As a result, asignificant amount of time can be saved using the inventive systems andmethods compared to the conventional approach.

The inventive systems and methods can allow the medical device expansionto occur while the expander mechanisms, such as a mandrel, remainheated. That is, the medical device can be positioned on the expandermechanism, expanded, heat set, and then removed from the expandermechanism, all while the expander mechanism is maintained at the desiredheat-set temperature. This can save energy, as well as an additionalamount of time that would otherwise be required to cool and then reheatthe expander mechanisms, as is done in the conventional approach.

The steps of the methods are repeatable and reduce the possibility ofincorrectly expanding medical devices during the manufacturing process.The steps of the methods can be automated. Further, the methods providedherein can reduce the possibility of undesired torque, tension,expansion and compression of the medical device during manufacture.

Reference will now be made to figures wherein like structures will beprovided with like reference designations. It is understood that thedrawings are diagrammatic and schematic representations of exemplaryembodiments of the invention, and are not limiting of the presentinvention, nor are they necessarily drawn to scale.

FIGS. 1 and 2 illustrate one embodiment of a system 100 for expanding amedical device 102, such as a vascular device. For ease of reference, acoordinate system will be referenced in discussing system 100 thatincludes a central axis C, as shown in FIG. 1. Elements that aregenerally parallel to central axis C will also be described as beinglongitudinally or axially oriented relative to central axis C whileelements that are generally transverse or perpendicular to central axisC will be described as being radially oriented relative to central axisC. In addition, movement parallel to central axis C may be referred toas axial movement. The direction indicated by arrow 104 that is parallelto central axis C will be considered herein as the “distal” directionand the opposite direction will be considered herein as the “proximal”direction. As such, axial movement in the proximal and distal directionsmay be referred to as proximal and distal movement, respectively. Insome embodiments, the distal direction will correspond to vertically“up” and the proximal direction will correspond to vertically “down,”and may alternatively be referred to as such.

In addition, to clarify the discussion, when specifically referring tomedical device 102 in the expanded state, the identifier 102′ may beused.

As shown in the schematic representation of FIG. 1, system 100 caninclude a support structure assembly 106, an advancement guide assembly108, a transport assembly guide 110, a transport driver assembly 112,and an advancement mechanism 114.

Support structure assembly 106 comprises a support structure 116 havingattached thereto (as schematically represented by solid lines), anexpander 118, a thermal chamber 120 and a pair of securing devices 122(122 a and 122 b). Expander 118, thermal chamber 120, and securingdevices 122 are secured to support structure 116 so as to remainsubstantially stationary when other portions of system 100 are moved.Support structure 116 can comprise a rack or any other type of rigidsupport structure that can provide support to expander 118, thermalchamber 120, and securing devices 122 during the use thereof.

Although discussion herein refers to support structure 116 and thoseitems attached to it remaining substantially stationary while otherportions of system 100 are moved, this should not be limiting. Forexample, in some embodiments, support structure 116 can be the portionof system 100 that moves while other portions remain substantiallystationary.

Expander 118 is used to expand medical device 102 by forcing medicaldevice 102 radially outward as medical device 102 moves distally withrespect to expander 118. Expander 118 can comprise a distal portion 124and a conical or frustoconical portion 126 extending proximally from theproximal end of distal portion 124.

In the depicted embodiment, the diameter of distal portion 124 remainssubstantially unchanged along the entire length of distal portion 124such that distal portion 124 is substantially cylindrical. However, ifdesired the diameter of distal portion 124 can instead vary along thelength thereof. For example, in one embodiment, the diameter of distalportion 124 decreases as distal portion 124 extends proximally towardsconical portion 126 causing distal portion to be tapered. Other shapesare also possible.

Conical portion 126 proximally tapers from the diameter at the proximalend of distal portion 124 to a diameter that can be the same or smallerthan the diameter of the unexpanded medical device 102. In someembodiments, conical portion 126 can proximally taper to a diameter thatis slightly greater than the diameter of the unexpanded medical device102. Conical portion 126 can include an alignment guide 127, such as anaperture extending thereinto, to help in aligning advancement guideassembly 108 therewith. In some embodiments, expander can comprise amandrel.

If desired, expander 118 can include guides positioned on the outersurface thereof to guide transport mechanisms of advancement guideassembly 108, as discussed below. For example, FIG. 3 shows oneembodiment of an expander 118 that has a plurality of transport guides132 formed on an outer surface 134 of expander 118. Transport guides 132can be distributed circumferentially about outer surface 134. Eachtransport guide 132 can extend longitudinally along expander 118 throughconical portion 126 and distal portion 124. Transport guides 132 can beconfigured to receive the transport mechanisms of advancement guideassembly 108 and guide the transport mechanisms as they move axially.Such a configuration can constrain the transport mechanisms and keepthem in a particular spatial orientation during expansion of the medicaldevice, thereby allowing for a uniform expansion of the medical device.

Various embodiments of expanders that can be used as expander 118, bothwith and without transport guides, can be found in U.S. patentapplication Ser. No. 13/490,225, entitled “APPARATUS, SYSTEMS ANDMETHODS FOR MEDICAL DEVICE EXPANSION” and filed on the same day as thepresent application by the present applicant, which is incorporatedherein by reference in its entirety. Other expanders, with and withouttransport guides, can also be used.

Returning to FIG. 1, thermal chamber 120 is used to preheat medicaldevice 102 and to continue to heat medical device 102 as medical device102 is expanded and heat set. That is, thermal chamber 120 heats medicaldevice 102 to one or more temperatures substantial enough to allowmedical device 102 to be expanded from its compressed configuration toits expanded configuration and to heat set medical device 102 in itsexpanded configuration. Thus, thermal chamber 120 is configured tomaintain medical device 102 at predetermined preheat, expansion, andheat set temperatures throughout the preheating, expansion, and heatsetting steps.

The predetermined preheat, expansion, and heat set temperatures can beconfigured to be different from each other or two or all three of thepredetermined temperatures can be the same. As such, thermal chamber 120can be configured to maintain medical device 102 at a same temperaturethroughout the preheating, expansion, and heat setting steps or to heatmedical device 102 to different temperatures for two or three of thesteps. If two or more different predetermined temperatures are desired,thermal chamber can be divided axially into two or three sections, eachset to a different predetermined temperature so that medical device 120can be heated to the respective predetermined temperatures as medicaldevice 120 moves axially between the sections during the preheating,expansion, and heat setting steps.

Thermal chamber 120 can have a port 128 at the proximal end of thermalchamber 120 through which medical device 102 can enter and exit chamber120, and can be large enough to encompass at least the proximal end ofexpander 118 and a portion of advancement guide assembly 108, as shown.Thermal chamber 120 can comprise any device that can produce andmaintain the necessary heat. For example, thermal chamber 120 cancomprise any type of oven, such as a natural convection oven, a forcedgas convection oven, or the like. Alternatively, thermal chamber 120 cancomprise a radio frequency (RF) or microwave heating device, a fluidizedheating bed using sand or salt or the like, or any other type of heatingchamber.

It is appreciated that thermal chamber is just one example of a meansfor heating medical device 102. Other means are also possible. Forexample, in some embodiments, thermal chamber 120 can be omitted and aheating device can be used that directs heat to the medical deviceand/or the expander 118 without the use of a thermal chamber, such as anRF or microwave heating device. In other embodiments, expander 118 canbe heated internally or physically attached to an external heatingdevice so as to be heated by conduction. In still other embodiments,thermal chamber 120 can be used in conjunction with other heatingdevices, such as an internally heated expander 118. Other combinationsare also possible. In sum, although the discussion herein is directed tothermal chamber 120 as the means for heating medical device 102, anyapparatus that can be used to heat medical device 102 can be used as themeans for heating medical device 102.

Securing devices 122 are used to secure transport assembly guide 110 tosupport structure 116 yet still allow the expanded medical device 102′to pass over transport assembly guide 110 after medical device 102 hasbeen heat set. To facilitate this, each securing device can selectivelyopen and close at different times so that, during use of system 100, atleast one of securing devices 122 is closed to secure transport assemblyguide 110. Each securing device 122 can comprise an apparatus, such as aclamp, that selectively secures transport assembly guide 110 to supportstructure 116. Various types of clamps can be used, as can other typesof securing devices that can selectively secure transport assembly guide110 to support structure 116 while selectively allowing expanded medicaldevice 102′ to pass therethrough.

In the depicted embodiment, a pair of clamps 122 a and 122 b are shown,each having a pair of mating clamp arms 130 that are movable between aclamping position and an open position. In the clamping position, clamparms 130 secure transport assembly guide 110 therebetween (see, e.g.,the position of clamp 122 b in FIG. 2); in the open position, assemblyguide 110 is free from clamp arms 130 (see, e.g., the position of clamp122 a in FIG. 2). The clamps 122 can be opened and closed in conjunctionwith one another to secure transport assembly guide 110 to supportstructure 116 while allowing expanded medical device 102′ to passtherethrough. It is appreciated that other numbers of clamps can beused. It is also appreciated that other means of securing transportassembly guide 110 to support structure 106 can alternatively be used.

Continuing with FIG. 1, advancement guide assembly 108 comprises anelongate advancement guide 140 having a transport assembly 142 extendingdistally from a distal end of advancement guide 140.

Advancement guide 140 is used to longitudinally align medical device 102with expander 118 as medical device 102 is advanced towards expander118. Advancement guide 140 can comprise a rod or other type of elongateapparatus that allows medical device 102 to be axially aligned withexpander 118 as medical device 102 is advanced towards expander 118, asdiscussed in detail below.

In addition to axial alignment, advancement guide 140 can also beconfigured to rotationally align with expander 118. This can bebeneficial, e.g., to ensure that transport mechanisms 146 (discussedbelow) are axially aligned with transport guides 132 of expander 118.Otherwise, undesired torque or other type of stress may be induced onthe transport mechanisms when the transport mechanisms are receivedand/or move within the transport guides during expansion of a medicaldevice, which could have a detrimental effect on the medical device.

In one example, one or more rotational alignment aids can be positionedon advancement guide 140 to ensure that advancement guide 140 isrotationally aligned with expander 118. In one embodiment, therotational alignment aids can be positioned on advancement guide 140 atthe longitudinal location thereof where advancement guide 140 is securedby securing devices 162. For example one or more channels, bores,tracks, flanges or the like can radially extend inward or outward fromthe surface of advancement guide 140 to engage with mating rotationalalignment aids on the securing devices.

For example, FIG. 4 shows one embodiment of an advancement guide 140 inwhich a pair of rotational alignment aids 138 in the form of channels orflat spots are positioned on either lateral side of advancement guide140. Each channel 138 is configured to receive a corresponding matingflange 139 positioned on arms 163 of securing device 162 when securingdevice 162 secures advancement guide 140. To become fully engaged witheach other, channel 138 and corresponding flange 139 can require aparticular rotational alignment with each other.

As a result, when securing device 162 is closed so that clamp arms 163are clamped onto advancement guide 140 and flanges 139 are receivedwithin channels 138, flanges 139 can cause advancement guide 140 torotate to the desired aligned position if advancement guide 140 is outof rotational alignment. Examples of rotational alignment aids that canbe used in the present invention can be found in U.S. patent applicationSer. No. 13/490,225, cited above. Other types of rotational alignmentaids can also be used.

Returning to FIG. 1, transport assembly 142 can be used to receivemedical device 102 from advancement guide 140 and to transport medicaldevice 102 over conical portion 126 of expander 118 and to distalportion 124. Transport assembly 142 can be attached to or integrallyformed with the distal end of advancement guide 140.

Transport assembly 142 can comprise an axial guide 144 extendingdistally from advancement guide 140 to axially align transport assembly142 with expander 118. Axial guide 144 is configured to engage withexpander 118. In one embodiment, axial guide 144 comprises a rod or thelike that is received within alignment guide 127 within conical portion126 of expander 118.

Transport assembly 142 can also comprise a plurality of transportmechanisms 146, extending distally from advancement guide 140. Transportmechanisms 146 can be used to provide a bearing-type surface for medicaldevice 102 and to separate at least a portion of medical device 102 fromexpander 118 during the expansion process to reduce or even eliminatefriction between medical device 102 and expander 118. The number oftransport mechanisms 146 can vary. The transport mechanisms 146 cancomprise wires, strips, ribbons, yarns, threads, rods, or otherstructures having the desired strength and rigidity, with associatedflexibility and resiliency to allow the structure to perform theintended function of transport mechanisms 146. Using materials that cansustain high temperatures can allow the medical device to be heattreated while on the transport mechanisms.

Transport mechanisms 146 can be circumferentially positioned about axialguide 144, if axial guide 144 is used. For example, FIG. 5 shows a crosssectional end view of one embodiment of transport assembly 142 extendingfrom advancement guide 140. In the depicted embodiment, each transportmechanism 146 comprises a wire, and the wires 146 are positionedcircumferentially about axial guide 144. The wires can be made of metalsor alloys, such as, but not limited to, stainless steel, titanium,tantalum, tungsten, or alloys thereof, nickle chromium (commonly knownas nichrome), quartz, glass, glass thread, polymers, or other hightemperature material.

As discussed above, a plurality of corresponding transport guides 132,such as recesses, grooves, channels, or the like, can becircumferentially positioned on expander 118, as shown in FIG. 3, toreceive transport mechanisms 146 and keep transport mechanisms 146uniformly spaced circumferentially around expander 118. Transportmechanisms can be sized to project above outer surface 134 of expander118 when received in transport guides 132.

As a result, medical device 102 can rest on transport mechanisms 146,and move with transport mechanisms as medical device 102 is moved overexpander 118. As such, transport mechanisms 146 can provide a separationbetween medical device 102 and expander 118 to reduce friction that mayotherwise occur between medical device 102 and expander 118 duringexpansion or manufacture of medical device 102. Because of the reducedfriction, medical device 102 can be expanded with less susceptibility toadverse effects such as compression, tension, fracturing, bending,uneven expansion, and the like.

Furthermore, because transport guides 132 can be uniformly spacedcircumferentially around expander 118, transport mechanisms 146, whichslide within transport guides 132, can ensure that medical device 102remains in a desired rotational orientation when medical device is beingexpanded, thereby preventing undesired torque, tension, and the likewhile allowing medical device 102 to uniformly expand. Examples oftransport mechanisms 146 that can be used in the present invention canbe found in U.S. patent application Ser. No. 13/490,225, cited above.Other types of transport mechanisms can also be used.

Returning to FIG. 1, a tensioning mechanism 148, such as a spring or thelike, can be positioned at the distal end 147 of each transportmechanism 146, if desired. Tensioning mechanism 148 can be used to biastransport mechanism 146 during use to aid in the expansion of medicaldevice 102. Tensioning mechanism 148 can comprise a spring or othermeans of providing a tension to transport mechanism 146 after transportmechanism 146 has been attached to a structure.

Transport assembly guide 110 is used to position transport mechanisms146 at the proximal end of expander 118. Transport assembly guide 110can comprise a tubular body with an inside surface 154 having a diametersized to allow unexpanded medical device 102 to pass inside therethroughand an outside surface having a diameter sized to allow expanded medicaldevice 102′ to pass thereover.

As noted above, transport mechanisms 146 can be configured to bereceived within transport guides 132 on expander 118 and extend axiallyalong expander 118. As such, transport mechanisms 146 expand radiallyoutward as they pass over conical portion 126 to the expanded diameterof distal portion 124. To prevent transport mechanisms 146 fromexpanding outward before they are received within the transport guides132, transport mechanisms 146 can pass through transport assembly guide110. The distal end of transport assembly guide 110 can be positionedadjacent conical portion 126 of expander 118. As such, the inner surface154 of transport assembly guide 110 can cause transport mechanisms 146to remain radially in position as transport mechanisms 146 are receivedwithin transport guides 132 on expander 118. As noted above, transportassembly guide 110 is secured to support structure 116 by transportassembly guide securing devices 122.

As discussed below, medical device 102 can be positioned within thedistal end of transport assembly guide 110 within thermal chamber 120during preheating of medical device 102. As such, thermal chamber 120can comprise a metal or other material that can conduct heat. Inaddition, or alternatively, thermal chamber 120 can be perforated toallow heat to flow into thermal chamber 120. Other types of materialsand configurations are also possible for thermal chamber 120.

Transport driver assembly 112 comprises a transport driver 160 havingone or more advancement securing devices 162 (162 a and 162 b) and atransport mechanisms guide 164 attached thereto.

Transport driver 160 is used to move advancement guide assembly 108distally with respect to support structure assembly 106. Transportdriver 160 can comprise a structure that allows advancement guideassembly 108 to be attached thereto and that can move axially withrespect to support structure assembly 106.

As discussed above, securing devices 162 are used to secure advancementguide assembly 108 to transport driver 160. Similar to securing devices122, securing devices 162 are designed to do this, yet still allow theexpanded medical device 102′ to pass therethrough after medical device102 has been heat set. As such, securing devices 162 can be similar tosecuring devices 122, discussed above, and can comprise the same type ofapparatuses as securing devices 122. For example, similar to securingdevices 122, securing devices 162 can comprise a pair of clamps 162 aand 162 b each having a pair of mating clamp arms 163 that are movablebetween a clamping position and an open position.

If one or more rotational alignment aids are positioned along the lengthof advancement guide 140, securing devices 162 can be configured tosecure those rotational alignment aids in a particular rotationalconfiguration to ensure that advancement guide 140 is rotationallyaligned in a desired manner, as discussed above. For example, in theembodiment depicted in FIG. 4, each clamp arm 163 of securing device 162can include a flange 139 configured to be received into channel 138 ofadvancement guide 140.

Returning to FIG. 1, transport mechanisms guide 164 is used to positiontransport mechanisms 146 on the distal portion 124 of expander 118.Transport mechanisms guide 164 can comprise a tubular body with aninside surface 166 having a diameter sized slightly larger than thediameter of distal portion 124 so as to constrain transport mechanisms146 within transport guides 132 on expander 118 when expander 118 ispositioned within transport mechanisms guide 164. If distal portion 124has a diameter that varies along its length, transport mechanisms guide146 can be designed to resiliently push radially inward so as to followthe contour of distal portion 124.

As noted above, transport mechanisms 146 extend radially outward as theypass over conical portion 126 to the expanded diameter of distal portion124. To prevent transport mechanisms 146 from extending further radiallyoutward after they have been expanded to the diameter of distal portion124 and thereby exit transport guides 132 (FIG. 3), transport mechanisms146 can pass through transport mechanisms guide 164. The proximal end oftransport mechanisms guide 164 can be positioned at or near the proximalend of distal portion 124 of expander 118. As such, the inner surface166 of transport mechanisms guide 164 can constrain transport mechanisms146 to remain radially in position within the transport guides astransport mechanisms 146 extend onto distal portion 124.

Transport mechanisms guide 164 is slidingly secured to support structuretransport driver 160 and configured to be axially movable a specifieddistance with respect to transport driver 160 to allow space on distalportion 124 for medical device 102 to be positioned for heat settingthereof. As perhaps best illustrated in FIG. 1, transport driver 160includes an annular channel 170 bounded by a proximal flange 174 and adistal flange 176. Transport mechanisms guide 164 has an outwardlyextending flange 168 that is received within channel 170 and is limitedto be able to axially move only between flanges 174 and 176.

Advancement mechanism 114 is used to advance medical device 102 distallyalong advancement guide assembly 108 toward expander 118. Advancementmechanism 114 can comprise a tubular device having an inner diametersized large enough so that advancement mechanism 114 can easily fit overand slide on advancement guide assembly 108 yet sized small enough to beable to contact an end of the unexpanded medical device 102 andselectively advance unexpanded medical device 102 in a distal direction.Advancement mechanism 114 can be removable from advancement guide 140 toallow the unexpanded medical device 102 to be positioned on advancementguide 140, as discussed below. Advancement mechanism 114 may include anoutwardly extending flange 172 or the like on the proximal end to aid inthe expansion method, as discussed below.

FIG. 2 illustrates the assembled system 100, ready to receive a medicaldevice. Support structure 116 of support structure assembly 106 has beenomitted from FIG. 2 for clarity sake. In addition, because a medicaldevice has not yet been positioned on the depicted system 100,advancement mechanism 114 is not yet positioned on advancement guideassembly 140.

To assemble system 100, advancement guide assembly 108 can be positionedon support structure assembly 106 so that the distal ends of axial guide144 and transport mechanisms 146 can pass through port 128 into thermalchamber 120. Advancement guide assembly 108 can be advanced so thataxial guide 144 can enter into alignment guide 127 on conical portion126 of expander 118 and transport mechanisms 146 can be received withintransport guides 132 on expander 118. As advancement guide assembly 108is distally advanced, transport mechanisms 146 can correspondingly slidedistally relative to expander 118 within transport guides 132.

Before or after advancement guide assembly 108 has been positionedwithin support structure assembly 106, transport assembly guide 110 canbe positioned adjacent conical portion 126 of expander 118 so thattransport assembly 106 passes therethrough. Transport assembly guide 110can be secured to support structure 116 by at least one of the securingdevices 122. For example, in the depicted embodiment, clamp 122 b is inthe closed position to secure transport assembly guide 110.

Transport driver assembly 112 can then be positioned so that advancementguide 140 of advancement guide assembly 108 is positioned between clamparms 163 of each securing device 162 and so that expander 118 andtransport mechanisms 146 extend through transport mechanisms guide 164.The distal ends 147 of each transport mechanism 146 can then be attachedto the distal end of transport driver 160 by welding, an adhesive, anattachment device, or any other attachment method or device known in theart.

To keep transport mechanisms 146 taut throughout the medical deviceexpansion process, a tension can be put on transport mechanisms 146 oncetransport mechanisms 146 have been attached to transport driver 160. Forexample, advancement guide 140 can be retracted proximally aftertransport mechanisms 146 are attached to transport driver 160, which cancause tensioning mechanism 148 to place a tension on each transportmechanism 146. Thereafter, advancement guide 140 should be secured by atleast one of the advancement securing devices 162 or the tension ontransport mechanisms 146 may cause advancement guide 140 to movedistally with respect to the tensioning mechanisms 148, therebyreleasing the tension. Securing devices 162 can engage rotationalalignment aids 138, if the rotational alignment aids are included onadvancement guide 140.

To aid in maintaining tension on transport mechanisms 146, each securingdevice 162 can be dead-weighted, if desired. That is, each securingdevice 162 can be attached to a weight or other device configured tocause a force on the securing device that is in the opposite directionas the force causing the tension.

Various types of medical devices can be expanded using the systemsdiscussed and envisioned herein. For example, various types of stentsand scaffolds can be expanded using the systems discussed and envisionedherein. In one embodiment, medical device 102 can include a materialmade from any of a variety of known suitable materials, such as ashape-memory material (“SMM”) or superelastic material. For example, theSMM can be shaped in a manner that allows for restriction to induce asubstantially tubular, linear orientation while within a delivery shaft(e.g., delivery catheter or encircling an expandable member), but canautomatically retain the memory shape of the medical device onceextended from the delivery shaft. SMMs can be shape-memory alloys(“SMA”) or superelastic metals comprised of metal alloys, orshape-memory plastics (“SMP”) comprised of polymers.

Examples of SMAs that can be used in medical device 102 include, but arenot limited to: copper-zinc-aluminum; copper-aluminum-nickel;nickel-titanium (“NiTi”) alloys known as nitinol; andcobalt-chromium-nickel alloys or cobalt-chromium-nickel-molybdenumalloys known as elgiloy. For example, the primary material of themedical device 102 can be of a NiTi alloy that forms superelasticnitinol. Additional materials can be added to the nitinol depending onthe desired characteristic.

Examples of SMPs that can be used in medical device 102 include, but arenot limited to: biodegradable polymers, such asoligo(ε-caprolactone)diol, oligo(ρ-dioxanone)diol, and non-biodegradablepolymers such as, polynorborene, polyisoprene, styrene butadiene,polyurethane-based materials, vinyl acetate-polyester-based compounds,and others yet to be determined. As such, any SMP can be used inaccordance with the present invention.

FIGS. 6-14 illustrate one embodiment of a method of expanding medicaldevice 102 using system 100. As with other method embodiments discussedor envisioned herein, while an exemplary order of steps will bedescribed in expanding the medical device, it will be appreciated thatthe steps may be performed in different orders, that additional stepsmay be included, and/or that steps may be omitted.

In addition, reference will be made to proximal and distal portions ofvarious elements as well as directions of movement. In general, theproximal direction is “down” when viewing FIGS. 6-14, as indicated byarrow 200 on FIG. 6, while the distal direction is “up”, as indicated byarrow 202. System 100 can be configured to operate in a verticalconfiguration, in which the distal direction corresponds to verticallyup, although this is not required.

Before expanding a medical device, the medical device must first beinitially cut out or otherwise formed. For example, the medical devicecan be laser cut from a tube having a diameter that is approximatelyequal to the desired diameter of the compressed (i.e., unexpanded)medical device. The tube can then be deburred to clean any imperfectionsdue to the cutting. Other initial forming methods may also be used.

Before a first medical device is expanded, thermal chamber 120 can beinitially energized and allowed to arrive at the desired temperature ortemperatures. The desired temperature(s) is/are whatever temperature(s)facilitate expansion and heat setting of the medical device. This can beaffected by the material of the medical device among other factors. Asnoted above, thermal chamber 410 can be configured to maintain medicaldevice 102 at a same predetermined temperature throughout preheating,expansion, and heat setting of medical device 102 or to heat medicaldevice 102 to different predetermined temperatures for two or three ofthe steps. In one embodiment, the thermal chamber can be between about450° C. to about 600° C. Of course, other temperature ranges can also beused. Once heated to the desired temperature or temperatures, thermalchamber 120 can be configured to maintain the desired temperature(s) sothat the elements remaining therein, such as portions of the expander118, the transport mechanisms 146, and the transport assembly guide 110,remain heated, even between expansions of different medical devices.This can save significant time and energy compared with conventionalmedical device expansion approaches.

Also before expanding the medical device, securing devices 122 and 162should be initially configured as desired. For example, if clamps areused as the securing devices, the clamps should be opened or closed toarrive at the desired initial configuration. Many different initialconfigurations are possible. For example, in the depicted embodiment,securing devices 122 a and 122 b are in the open and closed positions,respectively, and securing devices 162 a and 162 b are in the closed andopen positions, respectively. Although various initial configurationsare possible, at least one of securing devices 122 and at least one ofsecuring devices 162 should be in the closed position to ensure thattransport assembly guide 110 and advancement guide 140 are secured inplace in their desired positions relative to one another and relative toexpander 118.

As shown in FIG. 6, the process can begin by positioning medical device102 on the system. To do so, securing device 162 b is opened, if it isnot already in the open position, and medical device 102 is slid ontothe proximal end of advancement guide 140, followed by advancementmechanism 114. Thereafter, advancement guide 140 can be advanceddistally, as indicated by arrows 204, to push and thereby advancemedical device 102 distally. As noted above, to ensure that advancementguide 140 is secured in place, at least one of the securing devices 162a or 162 b should be in the closed position. Therefore, securing device162 a should be closed, if it is not already in the closed position,before clamp 162 b is opened to secure advancement guide 140.

Turning to FIG. 7, once medical device 102 and advancement mechanism 114are positioned on advancement guide 140, securing device 162 b can beclosed, as indicated by arrows 210 to secure advancement guide 140, andsecuring device 162 a can then be opened, as indicated by arrows 212.With securing device 162 a open, advancement mechanism 114 can beadvanced further distally, as indicated by arrows 214, to advancemedical device 102 into transport assembly guide 110 and onto theproximal end of transport assembly 142. Advancement mechanism 114 can beadvanced distally until the distal end of medical device 102 ispositioned adjacent the distal end of transport assembly guide 110.

A guide scale (not shown) can be positioned on the outside surface ofthe proximal end of transport assembly guide 110, if desired, to helpthe user know when medical device 102 has arrived at the desiredlocation. Based on the known lengths of medical device 102 and transportassembly guide 110, the user can know before beginning the expansionprocess how much of advancement mechanism 114 is required to bepositioned inside transport assembly guide 110 for medical device 102 tobe positioned at the distal end of transport assembly guide 110. Thescale can be used to determine when advancement mechanism 114 has beeninserted the appropriate distance into transport assembly guide 110. Foran automated process, an actuator or the like can be used to advanceadvancement mechanism 114 the desired distance. Other options are alsopossible.

When medical device 102 is positioned adjacent the distal end oftransport assembly guide 110 as shown in FIG. 7, medical device 102 canbe located within thermal chamber 120. As such, medical device 102 canbegin to be heated by thermal chamber 120 so as to preheat medicaldevice 102 to the predetermined preheat temperature before expansion isperformed. The amount of time it takes for medical device 102 to becomepreheated to the desired temperature is dependent on many factors. Forexample, the type of thermal chamber 120, and the thickness, mass andmaterial content of medical device 102, are just a few of the variablesthat may affect the amount of time required.

However, as noted above, the proximal end of expander 118, the distalend of transport assembly guide 110, and a portion of transport assembly142 can remain within thermal chamber 120 during the entire expansionprocess. As such, those devices can remain at the desired temperature(s)and facilitate a relatively quick transition by medical device 102 tothe desired temperature(s). That is, the only portion within thermalchamber 120 that is not already heated is medical device 102, andbecause medical device 102 typically has very little mass, medicaldevice 102 can become heated quickly.

Turning to FIG. 8, once medical device 102 has been preheated to thepredetermined preheat temperature, medical device 102 can be uniformlyexpanded using expander 118. To do so, transport driver 160 can beadvanced distally relative to support structure assembly 106, asindicated by arrows 220. Because advancement guide 140 is secured totransport driver 160 by securing device 162 b, the distal movement oftransport driver 160 also advances guide 140 distally relative tosupport structure assembly 106. If desired, securing device 162 a canalso be closed before movement of transport driver 160, as indicated byarrows 222, to further secure advancement guide 140 to transport driver160. However, this is not required. As noted above, only one securingdevice 162 a or 162 b needs to be closed to secure advancement guide 140to transport driver 160.

Because transport mechanisms 146 are attached to or integrally formedwith advancement guide 140 and attached to transport driver 160, thedistal movement of transport driver 160 also advances transportmechanisms 146 distally relative to expander 118. Furthermore, becauseexpander 118, thermal chamber 120, and transport assembly guide 110 canall be secured to support structure 116, those devices can remainstationary relative to transport driver 160 when transport driver 160moves. Thus, when transport driver 160 moves distally, it, along withadvancement guide 140 and transport mechanisms 146 move distallyrelative to expander 118, thermal chamber 120, and transport assemblyguide 110.

As a result, as transport driver 160 is advanced distally, transportmechanisms 146 move distally along transport guides 132 on expander 118.As transport mechanisms 146 move along transport guides 132, theportions of transport mechanisms 146 on which medical device 102 ispositioned move distally out of the distal end of transport assemblyguide 110, then radially outward at conical portion 126, as indicated byarrows 224. As the portions of transport mechanisms 146 distally move,friction between the inner surface of medical device 102 and the outersurface of transport mechanisms 146 draw medical device 102 out oftransport assembly guide 110 and onto conical portion 126 of expander118.

As discussed above, transport mechanisms 146 can act as a bearing-typesurface that support and guide medical device 102 while maintaining aseparation between medical device 102 and expander 118. As a result,medical device 102 can continue with transport mechanisms 146 astransport mechanisms 146 move radially outward on conical portion 126,with medical device 102 having little or no contact with expander 118.In this manner, transport mechanisms 146 can help reduce or eveneliminate frictional engagement between medical device 102 and expander118. As a result, the likelihood is reduced of damage to medical device102 from excessive stresses caused by the expander during expansion ofthe medical device.

During expansion of medical device 110, thermal chamber 120 can maintainmedical device 110 at the predetermined expansion temperature. Asdiscussed above, the predetermined expansion temperature can bedifferent than or equal to the predetermined preheat temperature.

To aid in advancing medical device 102 radially outward, advancementmechanism 114 can also be advanced in conjunction with transport driver160, as indicated by arrows 226, until the distal end of advancementmechanism 114 contacts or becomes adjacent to conical portion 126 ofexpander 118. Advancement of advancement mechanism 114 can beaccomplished by clamping or otherwise temporarily attaching advancementmechanism 114 to advancement guide 140 so that advancement mechanism 114moves distally with advancement guide 140. In manual systems,advancement mechanism 114 can simply be pressed against advancementguide 140. Of course, other temporary attachment devices and methods canalso be used.

To prevent advancement mechanism 114 from distally advancing too far,flange 172 or the like positioned on the proximal end of advancementmechanism 114 can catch on the proximal end of transport assembly guide110.

As transport driver 160 advances distally, proximal flange 174 alsoadvances distally, as indicated by arrows 228. However, becauseoutwardly extending flange 168 of transport mechanisms guide 164 canmove axially within annular channel 170, transport mechanisms guide 164can remain positioned axially so that inside surface 166 thereof canremain adjacent the proximal end of distal portion 124 of expander 118when medical device 102 is on conical portion 126. This can helpconstrain transport mechanisms 146 to remain within transport guides 132on expander 118.

Turning to FIG. 9, further distally advancing transport driver 160relative to support structure assembly 106, as indicated by arrows 230,causes advancement guide 140 and transport mechanisms 146 to alsoadvance further distally. Because medical device 102 is positioned ontransport mechanisms 146, distal and radially outward movement oftransport mechanisms 146 can cause medical device 102, due to frictionbetween medical device 102 and transport mechanisms 146, to also movedistally and uniformly radially outward, as indicated by arrows 232,until medical device 102 becomes positioned on distal portion 124 ofexpander 118, as shown in FIG. 9. In this position, medical device 102is in its expanded configuration.

In the expanded configuration, medical device 110 generally takes on theshape of distal portion 124. For example, in the depicted embodiment,distal portion 124 is substantially cylindrical, thereby causing medicaldevice 110 to also have a substantially cylindrical shape in theexpanded configuration. Alternatively, if a tapered medical device isdesired, a tapered expander can be used, as discussed above. Because ofthe tapered shape of distal portion 124, medical device 110 is caused toalso have a tapered shape in the expanded configuration. Other expandedmedical device shapes can also be obtained by using expanders havingdistal portions with corresponding shapes.

Just before medical device 102 moves onto distal portion 124, distalmovement of transport driver 160 causes proximal flange 174 that boundschannel 170 to bias against and distally push flange 168 of transportmechanisms guide 164. This causes transport mechanisms guide 164 toadvance distally, as indicated by arrows 234. The distal movement ofguide 164 creates space at the proximal end of distal section 124 ofexpander 118 for medical device 102 to become positioned thereat. Inthis manner, the proximal end of transport mechanisms guide 164 can bemoved out of the way so that medical device 102 can become positioned ondistal portion 124 of expander 118, as illustrated in FIG. 9.

Maintaining transport mechanisms guide 164 as close as possible to theproximal end of distal portion 124 of expander 118 can yield variousbenefits. For example, transport mechanisms 146 can be constrained toremain within the transport guides on expander 118 at the point wheretransport mechanisms 146 transition between conical portion 126 anddistal portion 124 of expander 118. That is, transport mechanisms guide164 can constrain transport mechanisms to remain within transport guides132 at or near the elbow between conical portion 126 and distal portion124 of expander 118. In conjunction therewith, transport assembly guide110, through which transport mechanisms 146 pass, similarly constraintransport mechanisms 146 at the proximal end of expander 118 astransport mechanisms 146 transition from transport assembly guide 110 totransport guides 132 on conical section 126 of expander 118.

Medical device 102 can be maintained in the expanded configuration onexpander 118 within thermal chamber 120 for a predetermined period oftime to heat set the medical device 102. During heat setting of medicaldevice 110, thermal chamber 120 can maintain medical device 110 at thepredetermined heat set temperature. As discussed above, thepredetermined heat set temperature can be different than or equal to thepredetermined expansion temperature and/or the predetermined preheattemperature.

The length of time required to heat set medical device 102 can vary,depending on many factors. For example, a few of the variables that mayaffect the amount of time required include: the type of thermal chamber120, the temperature at which medical device 102 is maintained, and thethickness, mass and material content of medical device 102. Of course,other variables may also affect the amount of time required. In oneembodiment, the desired heat-set time can vary between 0 seconds (i.e.,no time at all) and 15 minutes, or any time therebetween. Other heat-settimes are also possible.

Turning to FIG. 10, after medical device 102 has been expanded and heatset for the predetermined amount of time, the expanded medical device102′ can be removed from the system. To do so, transport driver 160 canbe retracted proximally to its original position, as indicated by arrows240. As transport driver 160 retracts proximally, transport mechanisms146 and advancement guide 140 also move proximally by virtue of theirattachment to transport driver 160.

Transport mechanisms 146 move along transport guides 132 in expander 118and into transport assembly guide 110 as transport mechanisms 146 moveproximally. As such, transport mechanisms 146 follow transport guides132 as transport guides 132 move radially inward at conical portion 126.The inner wall at the distal end of transport assembly guide 110 can aidin forcing transport mechanisms 146 inward, as noted above.Specifically, as transport mechanisms 146 enter into transport assemblyguide 110, the wall at the proximal end of transport assembly guide 110can provide an inward pressure on transport mechanisms 146, forcingtransport mechanisms 146 radially inward.

Because expanded medical device 102′ is positioned on transportmechanisms 146 on distal portion 124 of expander 118, proximal movementof transport mechanisms 146 also causes medical device 102′ to moveproximally. However, instead of following transport mechanisms 146radially inward at conical portion 126, expanded medical device 102′ canremain in its expanded configuration due to the heat setting that hastaken place.

As a result, expanded medical device 102′ can become disengaged fromtransport mechanisms 146 at conical portion 126. If system 100 isvertically oriented (i.e., the central axis is oriented vertically),expanded medical device 102′ can simply fall in a downward direction(i.e., proximally) due to gravity when medical device 102′ becomesdisengaged from transport mechanisms 146, as indicated by arrows 242.Due to the expanded configuration, medical device 102′ can pass overtransport assembly guide 110 and out of thermal chamber 120 through port128 until medical device 102′ comes into contact with one of thesecuring devices. In the depicted embodiment, securing device 122 a hasbeen closed before expanded medical device 102′ has become disengaged,as indicated by arrows 244. This can occur anytime before disengagement.As a result, medical device 102′ has been stopped and rests uponsecuring device 122 a.

If system 100 is not vertically oriented, means can be included to moveexpanded medical device 102′ proximally. For example, a conveyor belt, awire, or other type of apparatus can be used. As another example,because medical device 102′ is typically very light, a puff of air orother gas can alternatively be used. Other devices and/or methods ofmoving expanded medical device 102′ proximally can also be used. Ifdesired, a track can also be included to guide medical device 102′ alongits proximal path.

Because expanded medical device 102′ is no longer in thermal chamber 120expanded medical device 102′ begins to cool, even as the elements thatremain within thermal chamber 120 can remain heated. Before handlingexpanded medical device 102′, it should be allowed to sufficiently cool.To do this, expanded medical device 102′ can be allowed to remain atsecuring device 122 a or any of the other securing devices, discussedbelow, that prevent expanded medical device 102′ from being removed fromsystem 100 for a predetermined period of time. Similar to preheating,discussed above, the amount of time required to sufficiently coolexpanded medical device 102′ can vary, but is typically not long.

As transport driver 160 moves proximally to its original position,annular channel 170 also correspondingly moves proximally. As a result,flange 168 of transport mechanisms guide 164, which is positioned inannular channel 170, also moves proximally, thereby allowing transportmechanisms guide 164 to move to its original position at the proximalend of distal portion 124 of expander 118. If gravity is not sufficientenough to move transport mechanisms guide 164 to its original position,or if system 100 is not vertically oriented, distal flange 176 boundingchannel 170 can push proximally on flange 168 to help coax transportmechanisms guide 164 to its original position.

Turning to FIG. 11, securing device 122 a can be opened, as indicated byarrows 250, causing expanded medical device 102′ to move proximally tosecuring device 122 b, as indicated by arrows 252. Before securingdevice 122 a is opened, however, securing device 122 b should be closed,if it hasn't been already, to secure transport assembly 110 whilesecuring device 122 a is open.

As noted above, only one of securing devices 122 needs to be closed atany one time to maintain transport assembly guide 110 in its securedposition. As such, as long as securing device 122 b is closed, securingdevice 122 a can be opened at any time before expanded medical device102′ becomes disengaged from transport mechanisms 146. This can allowexpanded medical device 102′ to fall directly to securing device 122 bwithout being stopped by securing device 122 a, if desired.

Turning to FIG. 12, securing device 122 b can be opened, as indicated byarrows 260, causing expanded medical device 102′ to move proximally tosecuring device 162 a, as indicated by arrows 262. Before securingdevice 122 b is opened, however, securing device 122 a should be closed,as indicated by arrows 264, to secure transport assembly 110 whilesecuring device 122 b is open. If desired, flange 172 at proximal end oftransport assembly 110 can be sized radially larger than expandedmedical device 102′ so that flange 172 prevents medical device 102′ frommoving proximally past flange 172. In that embodiment, transportassembly 110 must be moved proximally for expanded medical device 102′to continue proximally.

Turning to FIG. 13, securing device 162 a can be opened, as indicated byarrows 270, causing expanded medical device 102′ to move proximally tosecuring device 162 b, as indicated by arrows 272. In addition,advancement mechanism 114 can also be moved proximally to securingdevice 162 b, as indicated by arrows 274. Before securing device 162 ais opened, however, securing device 162 b should be closed, if it hasn'tbeen already, to secure advancement guide assembly 108 while securingdevice 162 a is open.

As noted above, only one of securing devices 162 needs to be closed atany one time to maintain advancement guide assembly 108 in its securedposition. As such, as long as securing device 162 b is closed, securingdevice 162 a can be opened at any time before expanded medical device102′ moves proximally through securing device 122 b, if desired. Thiscan allow expanded medical device 102′ to fall directly to securingdevice 162 b without being stopped by securing device 162 a.

Turning to FIG. 14, securing device 162 b can be opened, as indicated byarrows 280, to allow expanded medical device 102′ and advancementmechanism 114 to be removed from advancement guide 140. Before securingdevice 162 b is opened, however, securing device 162 a should be closed,as indicated by arrows 282, to secure advancement guide assembly 108while securing device 162 b is open.

To ready system 100 to expand another medical device, the elementsthereof can be moved to the initial configuration. For example, in thedepicted embodiment, securing devices 122 a and 122 b are respectivelyopened and closed, as indicated by arrows 282 and 284, to arrive at theinitial configuration shown in FIG. 6. Of course, as noted above, otherinitial configurations are also possible. Care should be taken, however,to make sure that at least one of securing devices 122 and at least oneof securing devices 162 are in the closed position at any point in time.

As discussed above, thermal chamber 120 can remain heated throughout theexpansion and heat setting processes of medical device 102. In addition,thermal chamber 120 can remain heated during the time between when oneexpanded medical device is being removed from system 100 and the nextunexpanded medical device is being mounted on system 100. As such,thermal chamber 120 can remain heated at a substantially constanttemperature while expanding and heat setting a plurality of medicaldevices, thereby maintaining the proximal portion of expander 118positioned within thermal chamber 120 at a predetermined temperature foras long as system 100 is in use.

It is appreciated that the systems and methods discussed above can bemodified as desired. For example, steps can be added or taken away fromthe methods, and elements of the system can be modified for a desireduse. For example, in one embodiment, the transport guides can beomitted, if desired. In that embodiment, the surface of the expander canbe coated with a low-friction material and the transport mechanisms canslide directly on the surface of the expander. However, the transportmechanisms may vary from their rotational positions due to the lack oftransport guides. As another example, the transport mechanisms can beomitted, if desired. In that embodiment, the surface of the expander canbe coated with a low-friction material and the medical device can slidedirectly on the surface of the expander and be pushed to the expandedconfiguration by a modified advancement mechanism. However, the benefitsof using the transport mechanisms would be lost.

As another example, the thermal chamber can be filled with an inert gas,such as argon or helium, or a non-inert gas, such as ammonia, so themedical device will not be in contact with oxygen when the medicaldevice is heated. This can prevent oxidation and corrosion fromoccurring while the medical device is within the thermal chamber. Toalso prevent oxidation and corrosion from occurring while the medicaldevice is cooling, a cooling chamber full of the inert gas can bepositioned adjacent the thermal chamber so that the medical device canmove to the cooling chamber directly from the thermal chamber. In thatembodiment, securing device 122 a can be positioned between the thermaland cooling chamber to act as a door between the chambers, only openingto allow the medical device to pass between the chambers. In thismanner, securing device 122 a can act as a barrier to prevent the hotgas from heating the cool gas in the cooling chamber and the cool gasfrom chilling the hot gas in the thermal chamber.

The method described above can be performed manually, can be automated,or can have aspects of both. One of skill in the art would know how toautomate such equipment and therefore, with a few exceptions, has notbeen discussed herein.

The method described above can yield many benefits over conventionalsystems. For example, because the medical device can be completelyexpanded at one time without iterating through various expansion sizes,a significant amount of time and energy can be saved compared to theconventional approach.

Furthermore, the portions of the expander and transport assembly onwhich the medical device is positioned during the preheating andheat-setting steps can be maintained within the thermal chamber. As aresult, those portions only need to be brought up to the desiredtemperature once, when the system is turned on at the first of the day.After that, those portions can be maintained at the desired temperature;no time or energy is wasted in heating those portions after they havecooled off, because those portions are always heated. Because of this,the medical device is the only thing that must be heated each time, andbecause the medical device is typically very small with little mass, itcan quickly arrive at the desired temperature, thereby quickening theprocess and allowing many medical devices to be expanded per day.

In addition, because the transport mechanisms can act as a bearing-typesurface that support and guide the medical device while maintaining aseparation between the medical device and the expander, the transportmechanisms can help reduce or eliminate frictional engagement betweenthe medical device and the expander. As a result, the likelihood isreduced of damage to the medical device from excessive stresses causedby the expander during expansion of the medical device.

In addition, the processes can be automated, if desired, to increase thequantity and quality of expanded medical devices. Other benefits mayalso be possible using the systems and methods discussed and envisionedherein.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example,slight modifications of the mandrel are contemplated and possible andstill be within the spirit of the present invention and the scope of theclaims. The scope of the invention is, therefore, indicated by theappended claims rather than by the foregoing description.

What is claimed is:
 1. A method of manufacturing a medical device, themethod comprising: positioning a medical device on a plurality oftransport mechanisms supported by a preheated expander, the transportmechanisms being circumferentially arranged about a longitudinal axis;and radially moving the plurality of transport mechanism to advance themedical device over the preheated expander to uniformly expand themedical device, the preheated expander being maintained at apredetermined heat-setting temperature before and after the medicaldevice is uniformly expanded.
 2. The method of claim 1, wherein thepreheated expander comprises a plurality of transport guides.
 3. Themethod recited in claim 1, further comprising heat setting the expandedmedical for a predetermined period of time.
 4. The method recited inclaim 1, wherein the preheated expander is positioned within a thermalchamber that maintains the preheated expander at the predeterminedheat-setting temperature.
 5. The method recited in claim 1, furthercomprising advancing the medical device towards the preheated expanderbefore expanding the medical device.
 6. The method recited in claim 1,wherein the medical device is thermally coupled to the preheatedexpander and physically separated from the preheated expander when themedical device is positioned over the expander.
 7. The method recited inclaim 1, wherein the medical device is comprised of a shape-memorymaterial.
 8. A method of manufacturing a plurality of medical devices,the method comprising: performing the method of claim 1 for a firstmedical device using the preheated expander; removing the expanded firstmedical device from the preheated expander; performing the method ofclaim 1 for a second medical device using the preheated expander; andremoving the expanded second medical device from the preheated expander,the preheated expander maintaining the heat-setting temperaturethroughout expansion and removal of the first and second medicaldevices.
 9. A method of manufacturing a medical device, the methodcomprising: uniformly expanding a compressed medical device from a firstdiameter to a second diameter using a preheated expander, the medicaldevice being disposed on a plurality of transport mechanism that arecircumferentially arranged about a longitudinal axis of the preheatedexpander and radially move the medical device to uniformly expand themedical device; heat setting the expanded medical device at the seconddiameter while the medical device is positioned on the preheatedexpander; and removing the expanded medical device from the preheatedexpander, the steps of uniformly expanding the compressed medicaldevice, heat setting the expanded medical device, and removing theexpanded medical device all being performed while the preheated expanderis maintained at a predetermined heat-set temperature.
 10. A method ofmanufacturing a plurality of medical devices, the method comprising:performing the method of claim 9 for a first medical device using thepreheated expander; performing the method of claim 9 for a secondmedical device using the preheated expander, wherein the preheatedexpander is maintained at the predetermined heat-set temperaturethroughout expansion and removal of the first and second medicaldevices.
 11. A method of manufacturing a medical device, the methodcomprising: positioning a medical device on a plurality of transportmechanisms; advancing the transport mechanisms distally onto a preheatedexpander positioned within a thermal chamber, thereby causing themedical device to advance distally onto the preheated expander, thetransport mechanisms acting as a bearing-type surface that supports andguides the medical device while maintaining a separation between themedical device and the preheated expander; and uniformly expanding themedical device while the medical device is positioned on the preheatedexpander, the medical device becoming heat set when expanded due to thepreheated expander.
 12. The method recited in claim 11, furthercomprising preheating the unexpanded medical device in the thermalchamber while the medical device is positioned on the plurality oftransport mechanisms.
 13. The method recited in claim 12, furthercomprising removing the expanded medical device from the preheatedexpander by retracting the transport mechanisms proximally from thepreheated expander, thereby causing the medical device to retractproximally from the preheated expander.
 14. The method recited in claim12, wherein advancing the transport mechanisms distally onto thepreheated expander comprises advancing the transport mechanisms distallyon or in a plurality of transport guides formed on the preheatedexpander.
 15. The method recited in claim 14, wherein the plurality oftransport mechanisms comprises a plurality of wires and the plurality oftransport guides comprises a plurality of grooves that receive thewires, each groove being sized such that a portion of the wire receivetherein extends outward from the groove.
 16. The method recited in claim14, wherein the transport guides are positioned on a conical section ofthe preheated expander such that the transport mechanisms each moveradially outward from a central longitudinal axis of the preheatedexpander as the transport mechanisms advance distally in the transportguides, thereby causing the medical device to uniformly expand.